Edrophonium is used for the Tensilon test in suspected myasthenia gravis. Compared to neostigmine, edrophonium has all of the following characteristics EXCEPT:

• A Very rapid onset of action within 30–60 seconds
• B Suitable for long-term oral treatment of myasthenia gravis ✓
• C Very short duration of action (5–10 minutes)
• D Binds reversibly to anionic site of AChE without carbamylating the enzyme

Explanation

Edrophonium's ultra-short duration (5–10 minutes) is ideal for diagnostic purposes but makes it completely impractical for long-term maintenance therapy of myasthenia gravis. It acts by binding electrostatically to the anionic site of acetylcholinesterase without forming a covalent carbamyl-enzyme bond — a purely ionic interaction that explains its rapid reversibility. Neostigmine and pyridostigmine, with longer durations, are used for maintenance.

Reference: KD Tripathi, Essentials of Medical Pharmacology, 8th ed.

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Written and medically reviewed by the StethoPrep medical team.